1. Technical Field
This invention relates generally to a self-contained in-ground geothermal generator. This invention also relates to the effective use of geothermal energy.
2. State of the Art
Geothermal is a renewable energy source made possible by the same tectonic activity that causes local earthquakes and the rising of the Rocky Mountains. The earth's rigged outer shell, the lithosphere, rests upon the hotter and more plastic region of the upper mantle, below the crust, called the asthenosphere. The thickness of the earth's crust varies from a few miles to perhaps one hundred and fifty miles. Rock heated by magma deep below the surface boils water trapped in underground reservoirs—sometimes as hot as 700 degree F. Some of this hot geothermal water travels back up through faults and cracks and reaches the earth's surface as hot springs or geysers, but most of it stays deep underground, trapped in cracks and porous rock. This natural collection of hot water is called a geothermal reservoir. We already enjoy some of this activity via natural hot springs.
Presently, wells are drilled into the geothermal reservoirs to bring the hot water to the surface. At geothermal power plants, this hot water is piped to the surface. Then, after removing silica, steam is created and used to spin turbines to produce electricity. It's also a proven, relatively clean energy source. More than 30 nations sitting in earthquake and volcanic zones have extensively used geothermal power for decades.
Existing use of geothermal energy is limited with location. Geothermal resources are limited to the “shallow” hydrothermal reservoirs at the crustal plate boundaries. Much of the world is underlain (3-6 miles down), by hot dry rock—no water, but lots of heat.
The invention of the coal-burning steam engine revolutionized industrial production in the 18th c. and opened the way to the development of mechanized transport by rail and sea. The modern steam engine, using high-pressure superheated steam, remains a major source of electrical power and means of marine propulsion, though oil has replaced coil as the fuel in many installations and the reciprocating engine has given way to the steam turbines.
Modern wells, mostly used in the oil industry and geothermal plants, drilled using rotary drills, can achieve lengths of over 38,000 feet (12 000 meters). The well is created by drilling a hole 5 to 30 inches (13-76 cm) in diameter into the earth. Drilling technology is improving every day. The combination of drilling technology and tunneling technology can produce even better results and wider and deeper wells.
Accordingly, there is a need in the field of geothermal energy for an apparatus and method for effectively using the enormous heat resources of the earth's crust that are accessible by using current drilling technology.